Field of the Invention
This invention relates to tamper proof watthour meter enclosures and more particularly to a permanent locking arrangement including an irremovable fastener securing the watthour meter cover to a base assembly.
The universal use and exposure of watthour meters at every residential and business establishment where electricity is supplied subjects such meters to vandalism and tampering. Since the watthour meter registers the amount of electrical energy to be billed for, unauthorized attempts are made to tamper with the meter movement to reduce the watthour meter indications. One deterrent to physical destruction of the meter movement is a nonbreakable meter cover such as described and claimed in U.S. Pat. No. 3,846,677 issued Nov. 5, 1974, and assigned to the assignee of this invention.
Removal of conventional watthour meters from an associated meter socket permits separation of the meter cover from the base assembly to expose the meter movement to tampering. The following U.S. patents, disclose arrangements for locking the meter cover to the base assembly: U.S. Pat. No. 1,969,499, issued Aug. 7, 1973; U.S. Pat. No. 3,928,788, issued Dec. 23, 1975, assigned to the assignee of this invention, and U.S. Pat. No. 3,943,441 issued in Mar. 9, 1976.
In the U.S. Pat. No. 1,969,499 a resilient locking strip is mounted on the meter base assembly and is biased into slots formed in the inner periphery of the meter cover. A screw extending to the back of the base assembly is threaded further into the base to bias the locking strip into a cover slot. The screw is accessible from the rear of the base and can be reversely threaded to release the locking strip from the cover slot so that the arrangement does not permanently lock the cover to the base assembly.
In U.S. Pat. Nos. 3,846,677 and 3,943,441 clip arrangements are disposed which interlock the inner mating mounting surfaces of the meter cover and base assembly. A specially designed clip configuration is required for preventing unlocking rotation of the meter cover relative to the base assembly.